Variable curve jig for an intramedullary device

Abstract

The present invention relates to an apparatus for affixing intramedullary devices in a body. In particular the apparatus comprises a jig affixable to an intramedullary nail. There is also provided a method of determining the position of holes to be drilled through a bone which align with holes in the nail.

The invention claimed is: 
     
       1. An assembly comprising an apparatus for affixing an intramedullary device having a curved longitudinal profile, and the intramedullary device, the apparatus comprising:
 a jig affixable to the intramedullary device at a proximal end, the jig comprising:
 a guide arm having a proximal end and a distal end, the distal end being movable relative to the intramedullary device, the distal end movable between a non-aligned position in which the distal end is laterally spaced from a distal end of the intramedullary device, and an aligned position in which the distal end is aligned with the distal end of the intramedullary device, and 
 a second arm biased away from the guide arm in the aligned position; 
 
 a drill guide suitable for guiding an affixment towards the distal end of the intramedullary device, 
 an alignment adjuster to adjust an alignment of the guide arm relative to a longitudinal axis of the intramedullary device, 
 wherein in the non-aligned position, a longitudinal profile of the guide arm is curved between the proximal end and the distal end, wherein the curve of the longitudinal profile of the guide arm varies between the non-aligned position and the aligned position. 
 
     
     
       2. The assembly as claimed in  claim 1 , wherein a radius of curvature of the curved longitudinal profile of the guide arm is smaller than a radius of curvature of the curved longitudinal profile of the intramedullary device, and the radius of curvature of the longitudinal profile of the guide arm is greater in the aligned position than in the non-aligned position. 
     
     
       3. The assembly as claimed in  claim 2 , wherein in the non-aligned position, the longitudinal profile of the guide arm extends arcuately from the proximal end to the distal end away from the aligned position. 
     
     
       4. The assembly as claimed in  claim 2 , wherein in the non-aligned position, the radius of curvature of the guide arm is non-constant and varies at more than one point along its longitudinal profile, and the radius of curvature of the longitudinal profile of the guide arm is less than the radius of curvature of the longitudinal profile of the intramedullary device at each variation. 
     
     
       5. The assembly as claimed in  claim 4 , wherein the radius of curvature of the longitudinal profile of the guide arm varies at two or more points along its longitudinal profile. 
     
     
       6. The assembly as claimed in  claim 4 , wherein the radius of curvature alters within 50% of a length of the guide arm towards the proximal end. 
     
     
       7. The assembly as claimed in  claim 4 , wherein the radius of curvature alters within 30% of a length of the guide arm towards the proximal end and within 30% of the length of the guide arm towards the distal end. 
     
     
       8. The assembly as claimed in  claim 2 , wherein a maximum spacing between the guide arm and the second arm is in the non-aligned position. 
     
     
       9. The assembly as claimed in  claim 1 , wherein in the non-aligned position, a radius of curvature of the longitudinal profile of the guide arm is at least 10% less than a radius of curvature of the longitudinal profile of the intramedullary device. 
     
     
       10. The assembly as claimed in  claim 1 , wherein a radius of curvature of the curved longitudinal profile of the guide arm is greater than a radius of curvature of the curved longitudinal profile of the intramedullary device, and the radius of curvature of the longitudinal profile of the guide arm is smaller in the aligned position than the radius of curvature of the longitudinal profile of the guide arm in the non-aligned position. 
     
     
       11. The assembly as claimed in  claim 10 , wherein in the non-aligned position, the radius of curvature of the longitudinal profile of the guide arm is at least 10% greater than the radius of curvature of the longitudinal profile of the intramedullary device. 
     
     
       12. The assembly as claimed in  claim 10 , wherein in the non-aligned position, the radius of curvature of the guide arm is non-constant and varies at more than one point along its longitudinal profile, and the radius of curvature of the longitudinal profile of the guide arm is greater than the radius of curvature of the longitudinal profile of the intramedullary device at each variation. 
     
     
       13. The assembly as claimed in  claim 10 , wherein a minimum spacing between the guide arm and the second arm is in the non-aligned position. 
     
     
       14. The assembly claimed in  claim 1 , further comprising a radio translucent portion and at least one radio opaque marking at or towards the distal end. 
     
     
       15. The assembly as claimed in  claim 1 , wherein movement of the guide arm between the non-aligned and the aligned position occurs in a substantially lateral plane relative to the intramedullary device. 
     
     
       16. The assembly as claimed in  claim 1 , wherein the alignment adjuster is mounted around or through the second arm and is fixedly attached to the guide arm. 
     
     
       17. The assembly as claimed in  claim 1 , wherein the second arm is at least twice as rigid as the guide arm. 
     
     
       18. A kit of parts including the assembly as claimed in  claim 1  and instructions for use. 
     
     
       19. A system including the assembly as claimed in  claim 1 , and an analytical instrument used to monitor the alignment of the longitudinal axis of the guide arm relative to the longitudinal axis of the intramedullary device and a suitably programmed computer.